Meanwhile bring a medium pot of lightly salted water to a boil. Add orzo and cook as package directs; drain.

While pasta cooks, coat a large nonstick skillet with nonstick spray; heat over medium heat. Add beef, onion, fennel seeds and oregano. Cook 6 minutes, breaking up meat with a wooden spoon, until beef is browned and onions are tender. Remove from heat.

Add orzo, tomatoes with their juices, and mozzarella to skillet; toss to mix, then fill peppers. Bake 5 minutes or until cheese melts. Sprinkle with basil.